1. Field
The present invention generally relates to surge protectors and improvements thereof. More particularly, the present invention relates to surge protectors capable of consistent fail open functionality and improvements thereof.
2. Description of the Related Art
Communications equipment, computers, home stereo amplifiers, televisions and other electronic devices are increasingly manufactured using a variety of electronic components that are vulnerable to damage from electrical energy surges. Surge variations in power and transmission line voltages, as well as noise, can change the operating frequency range of connected equipment and severely damage or destroy electronic devices. Electronic devices impacted by these surge conditions can be very expensive to repair or replace. Therefore, a cost effective way to protect these devices and components from power surges is needed.
One common problem in protecting electronic systems, devices and components from power surges is the unpredictable failure states of many currently utilized surge protection solutions. This is because the surge protection used in such systems, devices and components typically incorporate components that have erratic failure states. For example, a diode protection scheme utilized for a communication system may fail as a short at one surge current, but fail open under alternative surge or environmental conditions. Gas tubes, metal oxide varistors (MOVs), diodes, sidactors and other voltage or current limiting devices can similarly exhibit differing failure modes depending upon the environment, system and/or exposure to particular surge currents or voltages.
Fuses, exhibiting a predictable open failure state, have been implemented as safety components in communication or other electronic systems. A fuse is a device that will fail open once it has been exposed to high enough current over a given period of time. However, fuses are not very accurate with respect to performance under short surge duration events. In addition, fuses have extreme performance variations over temperature. For example, a fuse in −40 degree Celsius temperature will take a relatively long time period to fail in the open state. Thus, fuses represent a less than ideal solution for surge protection or suppression despite their heightened failure state predictability.
In addition to fuses, circuit breakers and ground fault interrupt (GFI) circuits are other examples of devices that fail with a predictable open state. Unfortunately, circuit breakers are slow in reaction and tend to let through the majority of surge currents present. GFI circuits look for differential current flow through the circuit wires and do not activate if the surge currents flow through both of the circuit wires. These limitations of circuit breakers and GFI circuits, similar to fuses, yield inadequate surge protection solutions for many systems. The lacking surge protection characteristics of such devices outweigh their predictability in failure states and make them unacceptable for many system or device protection schemes.
Therefore, it is important for many electrical systems to fail in a predictable open condition for a variety of safety reasons. It is undesirable for a surge protection device to take down or render ineffective or inoperable an entire electrical system when only one node of the system is affected. In light of the above described limitations, the current state of the art for fail open devices have undesirable limitations that prove unsuccessful in adequately limiting surge currents and thus cannot sufficiently protect the connected equipment. Ideally, a surge protection device would offer adequate surge protection to a connected system while failing in an open failure state. It would thus be desirable to have a surge protection device that has a predictable or consistent open failure mode.